1. Field of the Invention
This invention generally relates to the field of footwear and more particularly to athletic footwear. Specifically, the present invention relates to athletic footwear which incorporate at least one cushioning bladder for adjusting the comfort and fit of the shoe, and auxiliary apparatus which augments the effectiveness of said bladder.
2. Description of the Prior Art
A typical athletic shoe includes an outsole, a midsole overlying the outsole, and an upper secured to the midsole. The midsole is generally made of a resilient foam material, such as ethylene vinyl acetate (EVA) or polyurethane (PU), which provides at least some cushioning and support to the athlete's foot. Some midsoles have recesses formed therein for containing resilient pads or fluid filled bladders. Fluid filled bladders are frequently positioned in the heel areas of shoe soles since, in a normal walking or running gait, the heel area of the foot usually strikes the ground first at each footfall. However, fluid filled bladders or cushioning pads may be positioned in other areas of the shoe and shoe sole that accept significant external forces during use.
Many prior art fluid filled bladders have been filled with a gas, such as air, while others have been filled with liquids or viscous gels. Air filled bladders provide good shock absorption of relatively light external loads through compression of the air. As the air compresses, the resistance of the bladder increases. However, one disadvantage of prior art air filled bladders is that they fail to provide adequate shock absorption in response to extreme external forces. Under extreme loads, the walls of air filled bladders have a tendency to "bottom out" against one another. Thus, there is a need for a cushioning system that provides good shock absorption in response to light external loads, and which is capable of accepting extreme loads with minimal propensity toward "bottoming out."
Another disadvantage of prior art air filled bladders is that they have a tendency to lose air. The typical plastic bladder allows some permeation of air. When a higher air pressure exists on the inside of the bladder, which is usually the case during normal loading of the shoe sole, the air contained within the bladder tends to leak through the bladder walls over time.
In order to increase both the comfort and fit of the footwear, manufacturers have incorporated inflatable bladders of various designs into the construction of the footwear. The development, incorporation, and use of inflatable air bladders within athletic footwear was and is particularly appropriate for ski boots used for downhill skiing. Thus, a number of patents relate to the field of ski boots which incorporate inflatable air bladders, for example, German Patent No. 2,162,619, and more recently U.S. Pat. No. 4,662,087. While the original designs for ski boots having air bladders incorporated the use of an external pressurizing device such as a hand pump, more recent designs incorporate the design of the pump into the article of footwear, such as for example the ski boot of U.S. Pat. No. 4,702,022.
The demands for comfort and snugness of fit in other athletic events has resulted in the use of the inflatable bladders originally developed for ski boots in various types of athletic footwear, including athletic shoes used for basketball and other sports. There are presently available athletic shoes incorporating an air pump, such as depicted within U.S. Pat. No. 5,074,765, to inflate air bladders located within the sole of the shoe, or alternatively, bladders located in portions of the upper or the tongue of the athletic shoe. The advantages of these types of shoes is manifested primarily by their increased comfort and the secure positioning or fit of the foot within the shoe. Another benefit derived from the use of air bladders is the potential for reduction of forces transmitted through the shoe to the foot and ankle of the wearer during performance of the athletic endeavor. Thus, current athletic shoes having incorporated air bladders provide enhanced comfort and fit, while also reducing the occurrence of various types of injuries.
For the athletic shoes currently available which incorporate both the inflatable air bladders and a pump inflation means, the comfort and fit of the article of footwear is adjusted by inflating the air bladder by use of the pump after securing the footwear about the foot. The wearer simply inflates the air bladder until a particular pressure level, or fit, is felt by the foot. A pressure gauge may be associated with such shoes, as disclosed in U.S. Pat. No. 5,588,227 to facilitate consistent pressurization.
Although shoes of the aforesaid nature provide shock-absorbing effectiveness, the limited space available within the sole for a bladder causes compromises with respect to adjustability of effect versus the bottoming out phenomenon.
It is accordingly an object of the present invention to provide a shoe cushioning system which utilizes auxiliary apparatus to augment the effectiveness of a bladder within an athletic shoe.
It is a further object of this invention to provide apparatus as in the foregoing object that permits adjustability of the response of the bladder to impact forces.
It is another object of the present invention to provide apparatus of the aforesaid nature which is easily attached to and removed from an athletic shoe.
It is a still further object of this invention to provide apparatus of the aforesaid nature of simple, durable construction amenable to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.